The interest on the application of the shot peening process to arrest and/or delay crack growth is rising. The main effect of the shot peening technique is to introduce a residual stress field that increases the working life of mechanical components. In this paper, it is presented the numerical simulation (FEM) of the shot peening process and the effect of introducing a residual stress field. Besides, the consequence of changing the sizes of the impacting ball is analyzed. This work also used the Crack Compliance Method (CCM) for the determination of residual stresses in beams subjected to a numerical simulation of a shot peening process. The numerical results obtained provide a quantitative demonstration of the effect of shot peening on the introduction of residual stresses by using different sizes of impacting balls and assess the efficiency of the CCM.